Nike
But the inspiring phrase had a surprising origin - a convicted murderer named Gary Gilmore, according to The New York Post.
Gilmore was convicted of murdering a convenience store clerk and a motel manager.
When he faced execution by firing squad in 1977, Gilmore reportedly said "Let's do it!"
The line struck a chord with Nike marketing mastermind Dan Wieden a decade later.
At the time, Nike was trying to surpass Reebok as the top sneaker company.
"I was trying to write something that would tie it up so it could speak to women who had just started walking to get in shape to people who were world-class athletes - and it had the same kind of connection with them," Wieden told Dezeen magazine.
Gilmore suddenly came to mind.
"They asked him if he had any final thoughts and he said: 'Let's do it'. I didn't like 'Let's do it' so I just changed it to 'Just do it'," Wieden said.
After Nike debuted the slogan in a commercial about an 80-year-old runner in 1988, the brand's sales exploded.
A decade later, Nike's sales had gone from $877 million to $9.2 billion.
Nike's sales are expected to hit $28 billion this year.